For producing nuclear substituted anilines, a process has been found to be industrially advantageous in which a nuclear substituted benzene is brominated and the bromine atom of the resulting substituted bromobenzene is replaced with amino group by ammonolysis. In this case, however, possibility of the recovery and reuse of bromine in the waste liquid has a significant effect upon successfulness of this process.
Techniques for recovering bromine from various waste liquids also have long been known. Particularly with respect to the bromine recovery processes by acidifying and treating with chlorine the waste liquids containing bromine compounds to liberate bromine, several industrial processes, including the well-known Kubierschy's process and the latest one that was disclosed in U.S. Pat. No. 4,031,194, have been proposed and widely put to practical use. However, because the above-said waste liquids, which are objects to be treated in this invention, contain aniline derivatives, ammonia, and ammonium salts, chlorine treatment of the waste liquids in acidic region not only causes insolubilization of the aniline derivatives resulting in difficulty in stable operation but also involves danger of formation and accumulation of explosive trichloroamine (NCl.sub.3). Therefore, the recovery of bromine by chlorine treatment of the above-said waste liquid has been considered to be virtually impossible.
On the other hand, in the field of sewage treatment a process which comprises oxidative decomposition of ammonia contained in a small amount in a waste liquor by treating it with chlorine in an alkaline pH region is known as so-called Break Point Chlorination Process. However, the above-said waste liquid, which is the object of the treatment of this invention, contains such considerable amounts of aniline derivatives, ammonia, and ammonium salts that treatment thereof is troublesome and sometimes ammonia is still detected in the liquid even if it has been treated simply with chlorine in alkaline region, where the ammonia seems to have generated from the aniline derivatives.